indira gandhi national open university presents
DESCRIPTION
Indira Gandhi National Open University presents. A Video Lecture Course: Computer Platforms. BACKING STORAGE AND INTERFACING. Objectives. Define some backing storage technologies Discuss about the storage formats Discuss about the head mechanism of hard disks - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/1.jpg)
Indira Gandhi National Open University
presents
![Page 2: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/2.jpg)
A Video Lecture
Course:
Computer Platforms
![Page 3: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/3.jpg)
BACKING STORAGE
AND
INTERFACING
![Page 4: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/4.jpg)
Objectives
Define some backing storage technologies
Discuss about the storage formatsDiscuss about the head mechanism of
hard disksDefine some of the interfacing
mechanisms for backing storage
![Page 5: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/5.jpg)
What is Magnetic Disk?
A circular metal or plastic coated with magnetisable material
A mechanism using conducting coil which reads/write on disk: called head
Concentric tracks with width same as the head size
![Page 6: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/6.jpg)
Disk-data layout
![Page 7: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/7.jpg)
Why does Gap exist between adjacent tracks?
• To minimise errors due to Misalignments
• To minimise interference of magnetic fields
![Page 8: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/8.jpg)
The track on outermost side has same number of bits as the innermost track.
Density per linear inch increase as we move from outer to inner track
REASON: SIMPLE ELECTRONICS
![Page 9: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/9.jpg)
Data are stored in block-size region called SECTORS
– Typically 10-100 sectors/track
– To avoid unnecessary precision requirements on system, adjacent sectors are separated by intra track gaps
![Page 10: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/10.jpg)
How are sector position within a track identified?
• Control data for recording start and end of each sector and starting position on a track
• Example, 600 bytes are used for storing 512K data
![Page 11: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/11.jpg)
Head Motion:Fixed head - one/track.
Moveable head (one per surface)
Disk portability : Non removable/ Removable
Sides : Single/Double
Platter : Single/ Multiple
Some Characteristics of Disks
![Page 12: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/12.jpg)
Head Mechanism
• Contact (Floppy)
• Fixed gap
• Aerodynamic gap (Winchester)
![Page 13: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/13.jpg)
R A I D (Redundant Array of Independent Disks)
• A set of physical disk drives viewed as a single logical drive
• Data is distributed across the physical drives of an array
• Redundant disk capacity is used to guarantee data recoverability in case of a disk failure
![Page 14: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/14.jpg)
Optical Memory
• CD-ROM
• WORMs
• Erasable Optical Disks
![Page 15: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/15.jpg)
CD-ROMs
![Page 16: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/16.jpg)
CD-ROMs
• Appropriate for distribution of large amount of data to a large number of users
• High information storage capacity
• Mass replication is inexpensive
• Removable disks thus may be used for archival storages
![Page 17: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/17.jpg)
Disadvantages:
• Once fabricated cannot be changed
• Higher access time than disk
![Page 18: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/18.jpg)
WORMs
• Applicable for applications when small number of copies of a set of data is needed
• Disk can be written by a special writer once only
• WORMs are useful for archival storage of documents
![Page 19: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/19.jpg)
Erasable Optical Disk
• Can be read or written just like magnetic disk
• Technology is magnetic-optical system
• High Capacity
• Portable disks
• Reliable disks
• Use formats same as that of Hard disk
![Page 20: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/20.jpg)
Some Newer Storage Technologies
ZIP Drives• A high capacity floppy disk drive
developed by Image Corporation
• Hold about 100 MB of data
• Inexpensive and Durable
• Useful as a popular backing storage media
• Useful for transporting large files
![Page 21: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/21.jpg)
Digital Video Disks
• A new type of CD-ROMs
• Have a capacity of 4.7 GB to 17 GB
• Store movie date in MPEG-2 format
• Smaller and easier to store and durable
• Better picture quality and alternate sound Tracks
![Page 22: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/22.jpg)
Interfacing storage devices to The Computer
Why I/O Interfaces needed?
• For coordinating the flow of data between Internal resources and external devices
• Data buffering : To cater for the speed differences between the storage devices & CPU
• Error detection
![Page 23: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/23.jpg)
Communicates with System
through System or I/O bus
Communicates with devices
The Interface
![Page 24: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/24.jpg)
What is ESDI?
Enhanced Small Device Interface (ESDI) an interface standard for connecting disk drives to PCs.
ESDI controllers are needed to use ESDI disks
![Page 25: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/25.jpg)
What is IDE and Enhanced IDE?
• An interface for mass storage devices
• The controller is integrated into the disk or the drive
Intelligent Electronics or
Integrated Device Electronics
![Page 26: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/26.jpg)
• EIDE supports data rate between 4 Mbps to 16.6 Mbps three to four time faster then IDE
• EIDE can support mass storage up to 8.4 GB whereas IDE was up to 528 MB
![Page 27: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/27.jpg)
What is UDMA?
• Supports data transfer rates of 33.3 Mbps
• Twice as fast as previous disk standards for PCs
![Page 28: Indira Gandhi National Open University presents](https://reader035.vdocuments.net/reader035/viewer/2022081721/56814e45550346895dbbc119/html5/thumbnails/28.jpg)
SUM UP:
• The secondary storage technologies such as disks, CD-ROMs
• The data format of disks & CD-ROMs
• Head mechanisms for disks• The interface standards for storage
devices